So you're hardening them?
Won't tell a man what to do but there are several places that will heat-treat knife blades for knifemakers. If you call Magnus and ask real nicely what metal they use...or if they'll at least tell you what "class" the metal is in. You could send one a dozen or two to a place like that and tell them you want them at 53Rc or 59Rc. (Or a few of each if you want to find out where they get brittle.) Past 59Rc they're gonna be a PITA to sharpen.
Could you tell for sure they were harder than factory?
Got pictures of you stone setup? The one thing that keeps me from staying with 3 blades is the issues in getting the angles below 30. I've seen several contraptions but I can't "see" how the very tip gets sharpened at <30*.